If a dealer plate or registration sticker is lost, stolen, or destroyed, you must report the loss to DMV promptly and apply for a replacement. Do not continue operating vehicles under a plate number that has been reported as lost or stolen — if law enforcement runs the plate and it comes back as lost/stolen, the driver will be detained, and you’ll have a significant problem on your hands.
Document the circumstances of the loss — when you discovered it, where the plate was last known to be, whether you suspect theft. File a police report if you believe the plate was stolen. Keep copies of all reports and the replacement application in your records. This documentation protects you if the missing plate is later used in criminal activity — you can demonstrate that you reported it promptly and took appropriate steps.